From 0d8b704726047f4ce6323c491295ebee8223b275 Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Mon, 26 Jun 2006 00:25:57 -0700
Subject: [PATCH] --- yaml --- r: 30255 b: refs/heads/master c:
 5b0c1dd38b66e2dd0cf655aa845e341b50b93ddd h: refs/heads/master i:   30253:
 39a4db7ad80c1fac86f6c9d8d2ebe7a8513d8ff0   30251:
 bfe8c3e996d68aced951e55d88632aa4654756f6   30247:
 10a741ff3ef323add1b3e62d3a98f994ffd31604   30239:
 980766f129510d4268fca5eaab8cb6071094d439 v: v3

---
 [refs]               |  2 +-
 trunk/fs/proc/base.c | 29 ++++++++++++++++-------------
 2 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/[refs] b/[refs]
index 59bae5ed27a1..3ceb5377f99a 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 13b41b09491e5d75e8027dca1ee78f5e073bc4c0
+refs/heads/master: 5b0c1dd38b66e2dd0cf655aa845e341b50b93ddd
diff --git a/trunk/fs/proc/base.c b/trunk/fs/proc/base.c
index c7f855441573..f0db7f616ac3 100644
--- a/trunk/fs/proc/base.c
+++ b/trunk/fs/proc/base.c
@@ -1074,24 +1074,27 @@ static int proc_check_dentry_visible(struct inode *inode,
 	 * namespace, or are simply process local (like pipes).
 	 */
 	struct task_struct *task;
-	struct files_struct *task_files, *files;
 	int error = -EACCES;
 
 	/* See if the the two tasks share a commone set of
 	 * file descriptors.  If so everything is visible.
 	 */
-	task = get_proc_task(inode);
-	if (!task)
-		goto out;
-	files = get_files_struct(current);
-	task_files = get_files_struct(task);
-	if (files && task_files && (files == task_files))
-		error = 0;
-	if (task_files)
-		put_files_struct(task_files);
-	if (files)
-		put_files_struct(files);
-	put_task_struct(task);
+	rcu_read_lock();
+	task = tref_task(proc_tref(inode));
+	if (task) {
+		struct files_struct *task_files, *files;
+		/* This test answeres the question:
+		 * Is there a point in time since we looked up the
+		 * file descriptor where the two tasks share the
+		 * same files struct?
+		 */
+		rmb();
+		files = current->files;
+		task_files = task->files;
+		if (files && (files == task_files))
+			error = 0;
+	}
+	rcu_read_unlock();
 	if (!error)
 		goto out;